In this paper we present first LHCb results on charmless charged two- and three-body $B$ meson decays. In particular, using the first picobarn of integrated luminosity, LHCb observed the $B^{0}\rightarrow K^{+}π^{-}$ and $B^{+}\rightarrow K^{+}π^{+}π^{-}$ decays. Such decays provide an interesting way to determine the angle $γ$ of the Unitary Triangle, thanks to the possible presence of New Physics in the penguin loops.
Promising ways to search for New Physics effects in radiative penguin decays are in the angular analysis of $B_{d} \rightarrow K^{*0} μ^{+}μ^{-}$, in the measurement of direct CP violation in $\B_{d} \rightarrow K^{*0}μ^{+}μ^{-}$ and a time dependent analysis of $B_{s} \rightarrow ϕγ$. All of these studies are being pursued at LHCb. First results will be shown from the 2010 and early 2011 data, with particular emphasis on $B_{d} \rightarrow K^{*0} μ^{+}μ^{-}$.
Flavour changing neutral currents are only allowed via loop diagrams in the Standard Model (SM). Electroweak penguin processes are therefore sensitive probes for new physics, as physics beyond the Standard Model can enter via virtual particles at the same level as SM physics. The LHCb detector at the LHC with its forward geometry is ideally suited for the analysis of electroweak penguin processes in $B$ meson decays. All analyses are performed with 1 fb$^{-1}$ of collision data recorded at a centre-of-mass energy of 7 TeV in 2011 and constrain new physics models.
The study of CP violation in \Bs\, oscillations is a key measurement at the LHCb experiment. In this document, we discuss the latest LHCb results on the CP-violating phase, called $ϕ_s$, using \BsJKK\, and \BsJpipi\, channels. To conclude on the presence of New Physics in $ϕ_s$, the estimation of the sub-dominant contributions from the Standard Model becomes crucial now. We outline a method to estimate the contribution of penguin diagrams in $ϕ_s$. Branching fractions and upper limits of \BdKshh\,($ h^{(')}=K,π)$\, modes are presented.
Rare loop-induced decays are sensitive to New Physics in many Standard Model extensions. In this paper we discuss the potential of the LHCb experiment to very rare $\mathrm{B_s} \to μ^+ μ^-$ decays, radiative penguin $\mathrm{b \to s}γ$ decays and electroweak penguin $\mathrm{b \to s\ell\ell}$ decays. The experimental strategies and the expected sensitivities are presented.
The coupling of the electroweak gauge bosons of the Standard Model (SM) to leptons is flavour universal. Extensions of the SM do not necessarily have this property. Rare decays of heavy flavour are suppressed in the SM and new particles may give sizeable contributions to these processes, therefore, their precise study allows for sensitive tests of lepton flavour universality. Of particular interest are rare b to sll decays that are well accessible at the LHCb experiment. Recent results from LHCb on lepton flavour universality in rare b to sll decays are discussed.
The B^0_s -> J/psi K_S decay has recently been observed by the CDF collaboration and will be of interest for the LHCb experiment. It is the U-spin partner of the golden B^0_d -> J/psi K_S channel and offers a determination of the angle gamma of the unitarity triangle. Moreover, it allows us to control the hadronic penguin effects in the extraction of the B^0_d-\bar B^0_d mixing phase phi_d through a measurement of CP violation in B^0_d^0 -> J/psi K_S. We discuss the picture emerging for these measurements from an LHCb feasibility study. While LHCb will be able to extract gamma from the CP viol…
The analysis of the penguin decay Bd->K*MuMu at LHCb can act as a laboratory for the discovery and understanding of new physics. Through the Operator Product Expansion, the decay kinematics are well understood in both the Standard Model and in a large range of new physics scenarios. The theoretical errors from QCD effects can be characterized and a set of observables have been derived which minimise their influence in measurements. We will describe how these measurements can be made in LHCb with special emphasis on what can be done with a first run of the LHC with a few hundred pb-1 of integra…
The B_s^0 -> J/psi K_S decay has recently been observed by the CDF collaboration and will be of interest for the LHCb experiment. This channel will offer a new tool to extract the angle gamma of the unitarity triangle and to control doubly Cabibbo-suppressed penguin corrections to the determination of sin(2beta) from the well-known B_d^0 -> J/psi K_S mode with the help of the U-spin symmetry of strong interactions. While any competitive determination of gamma is interesting, the latter aspect is particularly relevant as LHCb will enter a territory of precision which makes the control of doubly…
Charmless $B$ decays are dominated by contributions from the short distance amplitudes from tree level and penguin loop-level amplitudes. The Tree contribution presents a weak phase $γ$. The relationship between these two amplitudes can generated a CP asymmetry depending from the relative amount among them in a particular decay. In multi-body charmless $B$ decays, these relative contribution can change along the phase space, given a non isotropic distribution of CP asymmetries in the Dalitz plot. Two recent LHCb analyses involving charmless multi-body B decays are discussed: the obsevation of …
We report on an indirect method being used to measure luminosity at LHCb. It involves recording the event rate of elastic diphoton dimuon production. Preliminary MC studies suggest that with 1 fb^{-1} of data this method could provide a luminosity measurement with a precision of better than 2%
B mesons provide an ideal laboratory for measurements of CP violation and searches for CP violation beyond the Standard Model. Recent measurements of the mixing phases of the $B_s^0$ and $B^0$ mesons, $ϕ_s$ and $\sin2β$, using decays to $J/ψX$ final states are presented. In view of future improved measurements, a good understanding of pollution from sub-leading penguin topologies in these decays is needed. Those can be probed using suppressed decays like $B_s^0 \to J/ψK_S^0$ and $B_s^0 \to J/ψ\overline{K}^{*0}$. Recent results using these decay modes are presented.
The LHCb and CDF Collaborations have recently reported evidence for a CP asymmetry around -0.7% in $ΔA_{CP}$, the difference between $A_{CP}(D^0 \to K^+ K^-)$ and $A_{CP}(D^0 \to π^+π^-)$. In the Standard Model this effect may be accounted for by enhanced $1/m_c$ corrections in a CP-violating penguin amplitude governed by a Cabibbo-Kobayashi-Maskawa (CKM) factor $V^*_{cb}V_{ub}$. A consistent scheme based on broken flavor SU(3) is presented relating Cabibbo-favored (CF) and singly-Cabibbo-suppressed (SCS) $D$ meson decay rates into two pseudoscalars. Two important ingredients supporting the ab…
The interference between Bs decay amplitudes to CP eigenstates Jpsi X directly or including Bs-Bsbar oscillation gives rise to a measurable CP violating phase phi_s. Here, a preliminary measurement of phi_s with Bs -> JpsiK+K- decays, and the measurement using Bs->Jpsipi+pi- decays, both obtained from a sample of 1/fb of pp collisions, collected by the LHCb experiment at a centre-of-mass energy sqrt{s}=7 TeV during 2011, are presented. In addition, the determination of the branching fraction and polarization fractions of Bs->JpsiKstbar, which can be used to constrain the contribution of sub-le…
Rare decays of heavy-flavoured particles provide an ideal laboratory to look for deviations from the Standard Model, and explore energy regimes beyond the LHC reach. Decays proceeding via electroweak penguin diagrams are excellent probes to search for New Physics, and $b \to s \ell^{+}\ell^{-}$ processes are particularly interesting since they give access to many observables such as branching fractions, asymmetries and angular observables. Recent results from the LHCb experiment are reviewed.
We examine new-physics (NP) effects in B decays with large b -> s penguin amplitudes. Decays involving b -> d penguins are assumed to be unaffected. We consider a model-independent parametrization of such NP. We argue that NP strong phases are negligible relative to those of the standard model. This allows us to describe the NP effects in terms of a small number of effective amplitudes A_NP^q (q=u,d,s,c) and corresponding weak phases Phi_q. We then consider pairs of neutral B decays which are related by flavour SU(3) in the standard model. One receives a large b -> s penguin component and has …
The $C\!P$-violating flavour-specific asymmetry in neutral $b$ mesons provides a method for testing the Standard Model. The measurements from the D0 experiment yield values of this asymmetry that disagree with the Standard Model at a level of 3.6 $σ$. This contribution discusses the latest LHCb measurements in this sector both from $B^0$ mesons ($a_{\mathrm{sl}}^d$) and $B^0_s$ mesons ($a_{\mathrm{sl}}^s$). Using their 2011 dataset, corresponding to an integrated luminosity of 1.0 $\mathrm{fb}^{-1}$ obtained in 2011, LHCb measured a value of $a_{\mathrm{sl}}^s = (-0.06 \pm 0.50_{\text{stat}} \…
We underline the theoretical interest of the vector-vector penguin decay $B_s \to ϕϕ$, very clean from the experimental point of view. The CP-violation asymmetry $A_{CP}^{mix}$ comes from the interference of mixing and decay $λ_{ϕϕ} = {q \over p} {\bar{A} \over A}$. In the Standard Model (SM) and in the Naive Factorization limit, the CP phase from the mixing ${q \over p}$ exactly cancels the CP phase from the decay ratio ${\bar{A} \over A}$. Therefore, this mode is suitable to look for possible New Physics (NP) because $A_{CP}^{mix}$ would directly indicate the departure from the SM in mixing.…
The Standard Model predicts a branching ratio for the decay mode Bs -> mu mu of (3.4 +/- 0.5)10e-9, while some SUSY models predict enhancements up to 2 orders of magnitude. It is expected that at the end of its life Tevatron will set and exclusion limit for this branching ratio of the order of 10e-8, leaving one order of magnitude to explore. The excellent vertex reconstruction, invariant mass resolution and muon identification of the LHCb detector make it well suited to observe a branching ratio in this range in the first years of running of LHC. In this article an overview of the analysis th…
The electroweak sector of the Standard Model contains three generations of charged leptons $\ell^-\in\{e^-,μ^-,τ^-\}$ as exact replicas of each other, except for their Yukawa couplings to the Higgs that determine their masses. The Yukawas, and thereby, the masses, are not predicted but are parameters in the theory. A basic tenet in the formalism, known as lepton universality, is equality of the couplings to the electroweak gauge bosons $\{γ, Z, W^-\}$ among all three generations, and has mostly stood the test of time. However, precision tests in $B$ decays have recently posed serious challenge…
The theoretical precision of the measurement of the $B^0_{d,s}$-$\bar B^0_{d,s}$ mixing phases $ϕ_{d,s}$ through the benchmark decays $B^0_d\to J/ψK_S$, $B^0_s\to J/ψϕ$ and $B^0_s\to J/ψf_0(980)$ is limited by doubly Cabibbo-suppressed penguin topologies which are usually neglected. However, the search for New-Physics effects in the quark-flavor sector has entered a territory where these effects have to be taken into account, which will be particularly relevant for the LHCb upgrade era. Thanks to their non-perturbative nature, the penguin corrections cannot be calculated but have rather to be …
Studies of semileptonic decays of b hadrons with the LHCb experiment are reported. In particular, measurements of the b hadron production fractions at the LHC and Bs semileptonic decays in P-wave charmed mesons are presented. An outlook of the LHCb potential in measuring the CKM matrix elements Vub and Vcb, as well as decays involving taus, is given.
Very recently, the LHCb Collaboration observed the $CP$ violation (CPV) in the charm sector for the first time, with $ΔA_{CP}^{\rm dir}\equiv A_{CP}(D^0\to K^+K^-)-A_{CP}(D^0\to π^+π^-)=(-1.54\pm0.29)\times10^{-3}$. This result is consistent with our prediction of $ΔA_{CP}^{\rm SM}=(-0.57\sim -1.87)\times 10^{-3}$ obtained in the factorization-assisted topological-amplitude (FAT) approach in [PRD86,036012(2012)]. It implies that the current understanding of the penguin dynamics in charm decays in the Standard Model is reasonable. Motivated by the success of the FAT approach, we further suggest…
The LHCb experiment has very recently presented new results on Lepton Universality Violation (LUV) in $B \to K^{(*)} \ell^+ \ell^-$ decays involving $K_S$ in the final state, which strengthens the recent evidence of LUV obtained in $B^+ \to K^{+} \ell^+ \ell^-$ decays and the previous measurements of $B \to K^{*0} \ell^+ \ell^-$. While LUV observables in the Standard Model are theoretically clean, their predictions in New Physics scenarios are sensitive to the details of the hadronic dynamics, and in particular of the charming penguin contribution. In this work, we show how a conservative trea…
We present the most general (six-helicity) angular analysis of Bs -> V_1 (-> P_1P'_1) V_2 (-> P_2P'_2) (V_i is a vector meson, and P_i, P'_i are pseudoscalars). We focus on final states accessible to both Bs and Bsbar -- these are mainly bbar -> sbar penguin decays. We also derive the most general decay amplitude, and discuss the differences between it and that used by LHCb in its analysis of Bs -> phi phi. In the standard model, all CP violation is predicted to be small, so that the simple measurement of a sizeable CP-violating observable indicates the presence of new physics. A full fit to t…
In 2017, LHCb collaboration reported their first observation of the rare decays $B_s \to ϕ(f_0(980)$ $/f_2(1270) \to ) π^+π^-$ and the evidence of $B^0 \to ϕ(f_0(980)/f_2(1270)\to)π^+π^-$. Motivated by this, we study these quasi-two-body decays in the perturbative QCD approach. The branching fractions, $CP$ asymmetries and the polarization fractions are calculated. We find that within the appropriate two-meson wave functions, the calculated branching fractions are in agreement with the measurements of LHCb. Based on the narrow-width approximation, We also calculate the branching fractions of t…
Direct CP violation in two-body $D\to PP$ and $D\to V\!P$ decays is studied within the framework of the topological amplitude approach for tree amplitudes and the QCD factorization approach for penguin amplitudes. It is the interference between tree and long-distance penguin and penguin-exchange amplitudes that pushes CP asymmetry difference between $D^0\to K^+K^-$ and $π^+π^-$ modes up to the per mille level. Using the same mechanism, we find that CP asymmetry can also occur at the $10^{-3}$ level in many of the $D\to V\!P$ channels or otherwise be negligibly small. There are six golden modes…
We study glueball $G$ production in gluonic penguin decay $B\to G + X_s$, using the next-to-leading order $b\to s g^*$ gluonic penguin interaction and effective couplings of a glueball to two perturbative gluons. Subsequent decays of a scalar glueball are described by using techniques of effective chiral Lagrangian to incorporate the interaction between a glueball and pseudoscalar mesons. Mixing effects between the pure glueball with other mesons are considered. Identifying the $f_0(1710)$ to be a scalar glueball, we find that both the top and charm penguin to be important and obtain a sizable…
Measurements of CP violation in $B^0_d\to J/ψK_{\rm S}^0$ and $B^0_s\to J/ψϕ$ decays play key roles in testing the quark-flavour sector of the Standard Model. The theoretical interpretation of the corresponding observables is limited by uncertainties from doubly Cabibbo-suppressed penguin topologies. With continuously increasing experimental precision, it is mandatory to get a handle on these contributions, which cannot be calculated reliably in QCD. In the case of the measurement of $\sin2β$ from $B^0_d\to J/ψK_{\rm S}^0$, the $U$-spin-related decay $B^0_s\to J/ψK_{\rm S}^0$ offers a tool to …
The LHCb experiment has the potential, during the 2010-11 run, to observe the rare decay $B^0_s\to μ^+μ^-$ or improve significantly its exclusion limits. This study will provide very sensitive probes of New Physics (NP) effects. High sensitivity to NP contributions is also achieved by measuring photon polarization by performing a time dependent analysis of $B^0_s \to ϕγ$, and by an angular study of the decay $B^0_d \to K^{*0}μ^+μ^-$. Preparations for these analyses are presented and studies shown of how existing data, for example prompt $J/ψ$ events, can be used to validate the analysis strate…
In the study of two-body charmless B decays as a mean of looking for direct CP-violation and measuring the CKM mixing parameters in the Standard Model, the short-distance penguin contribution with its absorptive part generated by charm quark loop seems capable of producing sufficient $B \to Kπ$ decays rates, as obtained in factorization and QCD-improved factorization models. However there are also long-distance charming penguin contributions which could give rise to a strong phase due to the rescattering $D^{*}D^{*}_{s} \to Kπ$ etc. In this talk, I would like to discuss recent works on the cha…
The penguin-dominated two-body weak decay of $Λ_b\rightarrow Λϕ$ is studied based on the perturbative QCD approach. In addition to the penguin emission diagrams, the penguin exchange and $W$ exchange ones are also accounted for. It is found that the penguin exchange contribution is in fact important and comparable to the penguin emission one, while the $W$ exchange contribution is highly Cabibbo-Kobayashi-Maskawa (CKM) suppressed. The predicted branching ratio, $\mathcal{B}(Λ_b\rightarrow Λϕ)=6.9^{+1.9+1.8}_{-2.0-1.6}\times10^{-6}$, is larger than the previous theoretical estimates but in comp…
We describe LHCb measurements for $D^0$--${\bar{D}}^0$ mixing parameters and searches for $CP$ violation using "wrong-sign" $D^0\to K^+π^-$ two-body decays. LHCb provides the world's most precise measurements of the mixing parameters to date, using 3 $fb^{-1}$ of $pp$ collision data. By measuring the mixing parameters separately for $D^0$ and ${\bar{D}}^0$, and allowing for $CP$ violation, the LHCb results also place the world's most stringent constraints on the $CP$ violation parameters, $|q/p|$ and $A_D$, from a single experiment.
Indirect CP violation in the $D^0$ system can be probed by measuring the parameter $A_Γ$, defined as the CP asymmetry of the effective lifetime of the $D^0$ meson decaying to a CP eigenstate. This can be significantly enhanced beyond Standard Model predictions by new physics. Measurements of $A_Γ$ using $D^0 \rightarrow K^+K^-$ and $D^0\rightarrow π^+π^-$ decays reconstructed from pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, are presented. The results are \begin{align*} A_Γ (ππ) = (+0.33 \pm 1.06 \pm 0.14) \times 10^{-3},\quad A_Γ …
Dalitz-plot analyses of $B\rightarrow Kππ$ decays provide direct access to decay amplitudes, and thereby weak and strong phases can be disentangled by resolving the interference patterns in phase space between intermediate resonant states. A phenomenological isospin analysis of $B\rightarrow K^*(\rightarrow Kπ)π$ decay amplitudes is presented exploiting available amplitude analyses performed at the Babar, Belle and LHCb experiments. A first application consists in constraining the CKM parameters thanks to an external hadronic input. A method, proposed some time ago by two different groups and …
The decay amplitude of $B^+\to π^+π^-π^+$ in the Dalitz plot has been analyzed by the LHCb using three different approaches for the $S$-wave component. It was found that the mode with $σ$ (or $f_0(500)$) exhibited a CP asymmetry of 15\% in the isobar model, whereas the $f_2(1270)$ mode had a 40\% asymmetry. On the contrary, CP asymmetry for the dominant quasi-two-body decay $B^-\toρ^0π^-$ was found to be consistent with zero in all three approaches, while all the existing theoretical predictions lead to a negative CP asymmetry ranging from $-7\%$ to $-45\%$. We show that the nearly vanishing C…
Motivated by the recent observation of CP violation in the charm sector by LHCb, we study direct CP asymmetries in the standard model (SM) for the singly Cabibbo-suppressed two-body hadronic decays of charmed mesons using the topological-diagram approach. In this approach, the magnitude and the phase of topological weak annihilation amplitudes which arise mainly from final-state rescattering can be extracted from the data. Consequently, direct CP asymmetry $a_{dir}^{\rm (tree)}$ at tree level can be reliably estimated. In general, it lies in the range $10^{-4}<a_{dir}^{\rm (tree)}<10^{-3}$. Sh…
LHCb, CDF and most recently Belle have observed a large difference between direct CP asymmetries in $D^0\to K^+K^-$ and $D^0\toπ^+π^-$. We use the measured value of $ΔA_{CP}$ to constrain the magnitude and strong phase of a QCD-enhanced standard model penguin and predict its effects on direct CP asymmetry in $D^0\toπ^0π^0$ and $D^+\to K^+\bar{K}^0$.
We investigate the CP-averaged branching ratios, the polarization fractions, the relative phases, and the CP-violating asymmetries of the penguin-dominated $B \to ϕK_1(1270) $ and $ ϕK_1(1400)$ decays in the perturbative QCD(pQCD) approach, where $K_1(1270)$ and $K_1(1400)$ are believed to be the mixtures of two distinct types of axial-vector $K_{1A}(^3P_1)$ and $K_{1B}(^1P_1)$ states with different behavior, however, their mixing angle $θ_{K_1}$ is still a hot and controversial topic presently. By numerical evaluations with two different mixing angles $θ_{K_1} \sim 33^\circ$ and $58^\circ$ an…
Various new measurements in charmless $B_{u,d,s}\to PP$ modes, where $P$ is a low lying pseudoscalar meson, are reported by Belle and LHCb. These include the rates of $B^0\toπ^0π^0$, $ηπ^0$, $B_s\toη'η'$, $B^0\to K^+K^-$ and $B^0_s\toπ^+π^-$ decays. Some of these modes are highly suppressed and are among the rarest $B$ decays. Direct CP asymmetries on various modes are constantly updated. It is well known that direct CP asymmetries and rates of suppressed modes are sensitive to final state interaction (FSI). As new measurements are reported and more data will be collected, it is interesting an…
The most common decay used for measuring 2beta_s, the phase of Bs-Bsbar mixing, is Bs -> J/psi phi. This decay is dominated by the colour-suppressed tree diagram, but there are other contributions due to gluonic and electroweak penguin diagrams. These are often referred to as "penguin pollution" (PP) because their inclusion in the amplitude leads to a theoretical error in the extraction of 2beta_s from the data. In the standard model (SM), it is estimated that the PP is negligible, but there is some uncertainty as to its exact size. Now, phi_s^{c\bar{c}s} (the measured value of 2beta_s) is sma…
We re-examine the question of measuring the weak phase gamma in B -> K pi pi decays. To this end, we express all B -> K pi pi amplitudes in terms of diagrams. We show that, as in B -> K pi, there exist relations between certain tree and electroweak-penguin diagrams. The imposition of these relations allows the extraction of gamma from measurements of the B -> K pi pi observables. We estimate the theoretical error in this method to be O(5%).
We show that ratios of tree and penguin amplitudes in B-> K*pi and B->rho K are two to three times larger than in B-> K pi. This allows for considerably larger CP asymmetries in the former processes than the 10% asymmetry measured in B0 -> K+pi-. We study isospin sum rules for rate asymmetries in B-> K pi, K*pi, rho K, estimating small violation from interference of tree and electroweak penguin amplitudes. The breaking of the K pi asymmetry sum rule is estimated to be one to two percent and negative. Violation of K*pi and rho K sum rules can be estimated from B->rho pi amplitudes using flavor …
We show that the CP-violating phases βand β' can respectively be determined from the time-dependent measurements of B_d \to D^*\pmD^\mp and B_s \to D^*\pm_sD^\mp_s decays, whose final states are non-CP eigenstates. The penguin contributions to the mixing-induced interference quantities are expected to be about 4% or smaller. We also point out two observables of O(1), which are pure functions of decay constants and form-factors, for a clean test of the factorization hypothesis in neutral-B decays into two heavy charmed mesons.
We show that, unlike other pure b -> d penguin processes, the decay Bs(t) -> phi K_s is dominated by a single amplitude, that of the internal t-quark. The contributions of the u- and c-quark operators each vanish due to a cancellation between the (V-A) \otimes (V-A) and (V-A) \otimes (V+A) matrix elements. Thus, the indirect CP asymmetry in this decay probes sin 2β. Although this cancellation is complete only for certain values of the s- and b-quark masses, the theoretical uncertainty on sin 2βis still less than 10% over most (~80%) of the parameter space. By measuring the direct CP asymmetry,…
Following the experimental results from LHCb on the rare decay $B^+_c \to K^-K^+π^+$, we investigate the possibility where this process is dominated by a double charm rescattering. The $B_c$ decay to double charm channels have a weak topology that is favoured in comparison with the direct production of $K^-K^+π^+$ in the final state, suppressed by quark annihilation. The decay amplitude for $B^+_c \to K^-K^+π^+$ with $B_c$ decaying first to double charm channels is described by a charm penguin diagram, represented by charm hadronic triangle loops, which reach the final state of interest after …
Within the factorization-assisted topological-amplitude approach, we studied the 33 charmless $B_{(s)} \to VV$ decays, where $V$ stands for a light vector meson. According to the flavor flows, the amplitude of each process can be decomposed into 8 different topologies. In contrast to the conventional flavor diagrammatic approach, we further factorize each topological amplitude into decay constant, form factors and unknown universal parameters. By $χ^2$ fitting 46 experimental observables, we extracted 10 theoretical parameters with $χ^2$ per degree of freedom around 2. Using the fitted paramet…
The decays $B_d^0\rightarrow D_d^-D_d^+$ and $B_s^0\rightarrow D_s^-D_s^+$ probe the CP-violating mixing phases $ϕ_d$ and $ϕ_s$, respectively. The theoretical uncertainty of the corresponding determinations is limited by contributions from penguin topologies, which can be included with the help of the $U$-spin symmetry of the strong interaction. We analyse the currently available data for $B^0_{d,s}\rightarrow D_{d,s}^-D_{d,s}^+$ decays and those with similar dynamics to constrain the involved non-perturbative parameters. Using further information from semileptonic $B_d^0\rightarrow D_d^-\ell^…
We show that the decay Bs -> J/psi f0(980), f0(980)->pi+ pi- can be used to measure the CP violating phase in Bs mixing, -2β_s, and estimate the sensitivity as +/- 0.050 rad, for 2/fb of LHCb data. After adding in the related Bs -> J/psi eta', η' -> rho gamma mode, the sensitivity improves to +/- 0.044 rad. Use of these CP eigenstates obviates the need for a transversity analysis that must be used in the case of Bs -> J/psi phi decays.
We present a new method for measuring the CP phase α. It requires the measurement of the pure penguin decays Bd(t) -> K(*) Kbar(*) and B_s -> K(*) Kbar(*). The method is quite clean: we estimate the theoretical uncertainty to be at most 5%. By applying the method to several K(*) Kbar(*) final states, αcan be extracted with a fourfold ambiguity. An additional assumption reduces this ambiguity to twofold: {α, α+ π}. Since no \pi0 detection is needed, this method can be used at hadron colliders.
We have studied extracting $|\vub/\vcb|$ by calculating the ratios ${\cal B}(\bar{B}^0\to D_s^{(*)-}(π^+,ρ^+))/{\cal B}(\bar{B}^0\to D_s^{(*)-}D^{(*)+})$ including penguin effects within the factorization assumption. The ratios involving $\bar{B}^0\to D_s^-D^{+}$ mode have considerable penguin corrections ($\sim 15%$ at the amplitude level), but those involving $\bar{B}^0\to D_s^-D^{*+}$ mode have relatively small penguin corrections. On the other hand, the $\bar{B}^0\to D_s^-D^{+}$ mode has smaller form-factor dependance. Therefore, these ratios complement each other in measuring $\vub/\vcb$.…
The Standard Model (SM) predicts that $ΔA_{\rm CP}$, the difference between the direct CP asymmetries for the modes $B^+\to π^0 K^+$ and $B^0\to π^- K^+$ that are related by weak isospin, should be close to zero. There has been a recent claim by the LHCb Collaboration that the measured value of $ΔA_{\rm CP}$ shows an uncomfortable tension with the SM prediction, almost at the $8σ$ level. Motivated by this claim, we critically re-examine the data on all the $B\to πK$ modes, including the CP asymmetries and CP-averaged branching fractions. From a combined Bayesian analysis with the topological a…
There is growing evidence for deviation from the standard model predictions in the ratios between semi-tauonic and semi-leptonic $B$ decays, known as the $R(D^{(*)})$ puzzle. If the source of this non-universality is new physics, it is natural to assume that it also breaks CP symmetry. In this paper we study the possibility of measuring CP violation in semi-tauonic $B$ decays, exploiting interference between excited charm mesons. Given the current values of $R(D^{(*)})$, we find that our proposed CP-violation observable could be as large as about 10%. We discuss the experimental advantages of …
Non-leptonic $B$ decays into charmless final states offer an important laboratory to study CP violation and the dynamics of strong interactions. Particularly interesting are $B^0_s\to K^-K^+$ and $B^0_d\toπ^-π^+$ decays, which are related by the $U$-spin symmetry of strong interactions, and allow for the extraction of CP-violating phases and tests of the Standard Model. The theoretical precision is limited by $U$-spin-breaking corrections and innovative methods are needed in view of the impressive future experimental precision expected in the era of Belle II and the LHCb upgrade. We have recen…
Direct CP violation in the hadronic charm decays provides a good testing ground for the Kobayashi-Maskawa mechanism in the Standard Model. Any significant deviations from the expectation would be indirect evidence of physics beyond the Standard Model. In view of improved measurements from LHCb and BESIII experiments, we re-analyze the Cabibbo-favored $D \to P\!P$ and $V\!P$ decays in the topological diagram approach. By assuming certain SU(3)-breaking effects in the tree-type amplitudes, we make predictions for both branching fractions and CP asymmetries of the singly Cabibbo-suppressed decay …
Studies of charmonium properties and production mechanism started with the discovery of $J/ψ$ meson. Since more than 40 years the charmonium production mechanism is still not entirely understood. Following the era of investigations at $e^+e^-$ machines, nowadays, charmonium states are copiously produced at hadron colliders, that allows systematic studies of their resonance parameters, production observables and decays. Despite large production rates, many charmonium states are barely studied due to the complications of their reconstruction against a large background level. The LHCb experiment …
Reconstruction of the $B^0 \to D^{*-} τ^+ ν_τ$ angular distribution is complicated by the strongly-biasing effect of losing the neutrino information from both the $B$ and $τ$ decays. In this work, a novel method for making unbiased measurements of the angular coefficients while preserving the model independence of the angular technique is demonstrated. The twelve angular functions that describe the signal decay, in addition to background terms, are modelled in a multidimensional fit, using template probability density functions that encapsulate all resolution and acceptance effects. Sensitivit…
Evidence of CP violation in the charm sector has been observed recently by the LHCb and CDF Collaborations. Adopting the topological diagram approach, we study flavor SU(3) symmetry breaking effects in the weak decay tree amplitudes of singly Cabibbo-suppressed $D\to PP$ decays. The symmetry breaking in the color-allowed and color-suppressed amplitudes is estimated with the help of the factorization ansatz, while that in the $W$-exchange amplitude is done by fitting to related branching fraction data. We find that the $W$-exchange amplitudes stay in the second quadrant relative to the color-al…
We present a detailed study of charmless two-body B decays into final states involving two vector mesons (VV) or two axial-vector mesons (AA) or one vector and one axial-vector meson (VA), within the framework of QCD factorization, where $A$ is either a $^3P_1$ or $^1P_1$ axial-vector meson. The main results are as follows. (i) In the presence of NLO nonfactorizable corrections, effective Wilson coefficients $a_i^h$ are helicity dependent. For some penguin-dominated modes, the constructive (destructive) interference in the negative-helicity (longitudinal-helicity) amplitude of the $B\to VV$ de…
